/**
 * 雪天
 */
export const snowFS: string = `uniform sampler2D colorTexture; //输入的场景渲染照片
 varying vec2 v_textureCoordinates;
 
 float snow(vec2 uv,float scale)
 {
     float time = czm_frameNumber / 60.0;
     float w=smoothstep(1.,0.,-uv.y*(scale/10.));if(w<.1)return 0.;
     uv+=time/scale;uv.y+=time*2./scale;uv.x+=sin(uv.y+time*.5)/scale;
     uv*=scale;vec2 s=floor(uv),f=fract(uv),p;float k=3.,d;
     p=.5+.35*sin(11.*fract(sin((s+p+scale)*mat2(7,3,6,5))*5.))-f;d=length(p);k=min(d,k);
     k=smoothstep(0.,k,sin(f.x+f.y)*0.01);
     return k*w;
 }
 
 void main(void){
     vec2 resolution = czm_viewport.zw;
     vec2 uv=(gl_FragCoord.xy*2.-resolution.xy)/min(resolution.x,resolution.y);
     vec3 finalColor=vec3(0);
     //float c=smoothstep(1.,0.3,clamp(uv.y*.3+.8,0.,.75));
     float c = 0.0;
     c+=snow(uv,30.);
     c+=snow(uv,20.);
     c+=snow(uv,15.);
     c+=snow(uv,10.);
     c+=snow(uv,8.);
     c+=snow(uv,6.);
     c+=snow(uv,5.);
     finalColor=(vec3(c)); //屏幕上雪的颜色
     gl_FragColor = mix(texture2D(colorTexture, v_textureCoordinates), vec4(finalColor,1), 0.2);  //将雪和三维场景融合
 
 }`;

 /**
  * 雨天
  */
export const rainFS = `uniform sampler2D colorTexture;//输入的场景渲染照片
 varying vec2 v_textureCoordinates;
 
 float hash(float x){
     return fract(sin(x*133.3)*13.13);
 }
 
 void main(void){
 
     float time = czm_frameNumber / 60.0;
     vec2 resolution = czm_viewport.zw;
 
     vec2 uv=(gl_FragCoord.xy*2.-resolution.xy)/min(resolution.x,resolution.y);
     vec3 c=vec3(.6,.7,.8);
 
     float a=-.4;
     float si=sin(a),co=cos(a);
     uv*=mat2(co,-si,si,co);
     uv*=length(uv+vec2(0,4.9))*.3+2.;
 
     float v=1.-sin(hash(floor(uv.x*100.))*2.);
     float b=clamp(abs(sin(20.*time*v+uv.y*(5./(2.+v))))-.95,0.,1.)*20.;
     c*=v*b; //屏幕上雨的颜色
 
     gl_FragColor = mix(texture2D(colorTexture, v_textureCoordinates), vec4(c,1), 0.15); //将雨和三维场景融合
 }`;

 /**
  * 雾天
  */
export const fogFS = 'uniform sampler2D colorTexture;\n'
+'  uniform sampler2D depthTexture;\n' 
+'  varying vec2 v_textureCoordinates;\n'
+'  void main(void)\n'
+'  {\n'
+'      vec4 origcolor=texture2D(colorTexture, v_textureCoordinates);\n'
+'      vec4 fogcolor=vec4(0.8,0.8,0.8,0.5);\n'
+'      float depth = czm_readDepth(depthTexture, v_textureCoordinates);\n'
+'      vec4 depthcolor=texture2D(depthTexture, v_textureCoordinates);\n'
+'      float f=(depthcolor.r-0.22)/1.7;\n'
+'      if(f<0.0) f=0.0;\n'
+'      else if(f>1.0) f=1.0;\n'
+'      gl_FragColor = mix(origcolor,fogcolor,f);\n'
+'   }';

/**
 * 阴天
 */
export const overcastFS = `uniform sampler2D colorTexture;//输入的场景渲染照片
 varying vec2 v_textureCoordinates;
 
 void main(void){
     gl_FragColor = mix(texture2D(colorTexture, v_textureCoordinates), vec4(0.5, 0.5, 0.5, 1.0), 0.5); //将阴和三维场景融合
 }`;